Variable length stent

ABSTRACT

A stent comprising a tubular member, a lumen extending through the tubular member, a first retention structure and a second retention structure at opposite ends of the tubular member. The first retention structure comprises multiple coils and a removable anti-coiling material over the multiple coils of the first retention structure to present the multiple coils as an elongated extension of the tubular member, whereupon removal of the removable anti-coiling material at least one of the multiple coils of the first retention structure is presented and any excess coils can be trimmed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of, and claims priority to andbenefit of co-pending claims the benefit of U.S. Non-provisionalapplication Ser. No. 16/504,511 entitled “Variable Length Stent,” filedJul. 8, 2019, which claimed priority from U.S. Provisional PatentApplication No. 62/748,627 filed Oct. 22, 2018, the contents of whichare incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to medical stents and particularly tovariable length stents.

BACKGROUND INFORMATION

Stents are well known and widely accepted as viable prostheses forbypassing obstructions and promoting drainage. Ureteral stents, forexample, function as a drainage tube between the renal pelvis of thekidney and the bladder. As the use of such stents has continued, it hasbeen found that various applications require stents of differentdiameters. Moreover, differences in individual anatomies require stentshaving different effective lengths between the end retention structures,such as the curved and helical coil portions located at the bladder andkidney ends of the stent as shown in the prior art. Consequently,hospitals and other facilities inventory stents of different diametersand for each diameter, stents of different lengths.

Referring to FIG. 1, a coronal view of a ureteral stent 11 of the priorart positioned in a renal pelvis 14 of a kidney 10 and a bladder 20 of aperson is shown. Kidney 10 drains urine into the renal pelvis 14, downthe ureter 18, out of the ureteral orifice 17, and into the bladder 20.During placement of ureteral stent 11, a guide wire (not shown) isnavigated through a cystoscope (not shown), through the ureteral orifice17, beyond any obstruction in ureter 18, into the renal pelvis 14 ofkidney 10. Stent 11 is then passed over this guidewire into the correctposition at which point the guidewire is removed and the stent 11 isleft in place. Stent 11 comprises a hollow tube that facilitates passageover the guidewire.

Stent 11 is designed with a bladder retention coil 24 for retainingstent 11 in the bladder 20 and a kidney retention coil 22 for retainingthe stent 11 in renal pelvis 14 of kidney 10. The area of stent 11between bladder retention coil 24 and kidney retention coil 22 is anintermediate portion 25. This is the non-coiled portion of the stent 11that varies in length.

Hospitals inventory ureteral stents of differing lengths dictated by thenon-coiled intermediate portion 25. The surgeon must choose the desiredlength prior to placement of stent 11. Stent 11 is also designed with atapered tip 13 on a proximal portion 32 of kidney retention coil 22 thatfacilitates passage of stent 11 beyond any obstructive pathology inureter 18. A distal portion 15 of bladder retention coil 24 is designedwith at least one hole 16 for phishing a retrieval string 35 to attachretrieval string 35 to distal portion 15 of bladder retention coil 24.Retrieval string 35 is often left emanating from the patient's urethra38 and can be extracted by the patient after a predetermined period oftime. Retrieval string 35 is typically only utilized following treatmentof the obstructive process.

Stent 11 is generally designed with a fixed diameter and fixed lengththat the surgeon must choose at the time of the procedure. Differentdiameters are chosen for various reasons at the surgeon's discretionbased on preference and certain pathologic processes. The length ofstent 11 is chosen based on the ureteral length. Often a patient'sheight is used as a surrogate to estimate the desired length. If stent11 is too short, stent 11 will not span the entirety of ureter 18 andresults in inadequate drainage of kidney 10. If stent 11 is too long,there is too much foreign material in either renal pelvis 14 or bladder20 resulting in additional stent symptomatology including flankdiscomfort, urinary urgency, urinary frequency, urinary incontinence andhematuria. To rectify placement of a stent 11 of inappropriate lengththe surgeon must remove stent 11 and place a new stent 11 of theappropriate length resulting in additional operating room costs.

Though not an all-inclusive list, typical diameters for ureteral stentsare 4.5, 6, 7 or 8 French (of the French Scale or French gauge).Likewise, though not all-inclusive, typical lengths of stents are 16,18, 20, 22, 24, 26 or 28 cm. In order for hospitals to carry a fullcomplement of stents, they must inventory stents with a combination ofthese diameters and lengths. These stents are manufactured with anexpiration date, thus hospitals often will not carry stents in theextremes of length for fear of expiration prior to usage. This poses aclinical problem for physicians since often patients present to theemergency room needing urgent decompression of an obstructed system. Ifa stent of an extreme of length is anticipated the procedure may not beperformed at the facility if they do not inventory these sizes.Certainly, a hospital can special order stents of a particular size, butusually the clinical situation does not provide the hospital enoughlead-time to do this in a clinically useful timeframe. Furthermore,there are even more drastic extremes of length that would occasionallybe useful to physicians but are almost universally not inventoried.Patients with a pelvic kidney or transplanted kidney would potentiallybenefit from even shorter ureteral stents. Conversely, patients with atortuous ureter secondary to long-term obstruction may benefit from aneven longer ureteral stent to accommodate the tortuosity of the ureter.

Multiple inventions have been patented to create a variable lengthureteral stent. However, the majority of these designs rely on aredundancy of stent material that is left indwelling at the time of theprocedure. As described above, any redundancy of stent material leftindwelling may result in additional patient discomfort. Other designsare over-engineered or are fundamentally different from a typicalureteral stent design as to not be truly clinically useful.

Accordingly, there is a need for a ureteral stent with a completelymodifiable length and the ability to trim redundant stent material. Thisaffords the physician the ability to intraoperatively place a stent ofthe ideal length, using a single product, for every patient. Theinvention also significantly decreases hospital stent inventory, sinceonly varied stent diameter would need to be inventoried. It has theadded benefit of being able to accommodate ureteral lengths at theextremes that almost universally are not inventoried by hospitals.

SUMMARY

A stent comprising a tubular member, a lumen extending through thetubular member, a first retention structure and a second retentionstructure at opposite ends of the tubular member is disclosed. The firstretention structure further comprises multiple coils each of which canhave substantially the same diameter to provide an anchor for the stent.The stent can include a removable anti-coiling material over themultiple coils of the first retention structure to present the multiplecoils as an elongated extension of the tubular member, whereupon removalof the removable anti-coiling material at least one of the multiplecoils of the first retention structure is presented and any excess coilscan be trimmed. The multiple coils can each be wound about a separateaxis or a common axis to provide an anchor for the stent.

The stent can also include multiple indices on the elongated extensionof the tubular member each of which demarcate a corresponding one of themultiple coils of the first retention structure. The multiple indicesmay each be circumferential perforations in the anti-coiling materialthat enables a stripping away of the anti-coiling material. The multipleindices may each be visual markings.

The anti-coiling material may be adapted for removal beginning from oneof the multiple indices to an end of the elongated extension of thetubular member to present at least one coil of the multiple coils of thefirst retention structure. In which case one or more of the multiplecoils is trimmable at a predetermined location to remove at least onecoil from the multiple coils of the first retention structure to presenta single coil of the multiple coils of the first retention structure.

The stent may also include a distal end on the second retentionstructure and a tapered tip on the distal end adapted for maneuveringthe second retention structure past an obstruction. The distal end canalso include an eyelet on the distal end of the tapered tip forreceiving a suture.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reading the following detailed description, takentogether with the drawings wherein:

FIG. 1 is a coronal view of a ureteral stent of the prior art positionedin a renal pelvis of a kidney and a bladder of a person.

FIG. 2A is a perspective view of a stent with a tubular memberconstructed in accordance with this disclosure.

FIG. 2B is a perspective view of a stent with a tubular member alsoconstructed in accordance with this disclosure.

FIG. 3 is a perspective view of the stent of FIGS. 2A and 2B with ananti-coiling material applied over a retention structure to present theretention structure as an elongated extension of the hollow tubularmember.

FIG. 4 is an enlarged cross-sectional view taken along the lines 4-4 inFIG. 3.

FIG. 5A is a perspective view of the stent of FIG. 3.

FIG. 5B is a perspective view of the stent of FIG. 5A showing a stripperto remove the anti-coiling material at a pre-determined location on theelongated extension of the tubular member.

FIG. 5C is a perspective view of the stent of FIG. 5B showing theanti-coiling material removed.

FIG. 5D is a perspective view of the stent of FIG. 5C showing the excesscoils removed.

FIG. 6A shows stent with a tubular member constructed in accordance withthis disclosure.

FIG. 6B shows the stent of FIG. 6A with an anti-coiling layer tostraighten the end.

FIG. 6C shows the stent of FIG. 6B with a series of circumferentialperforations through the anti-coiling layer.

FIG. 6D is a close-up view of area 6D in FIG. 6C.

FIG. 6E shows the stent of FIG. 6C bent to break one of the series ofcircumferential perforations.

FIG. 6F is close-up view of area 6D of FIG. 6E.

FIG. 6G shows the stent of FIG. 6E with a portion of the anti-coilinglayer removed.

FIG. 7A is a close-up view of the second retention structure of thestent of FIG. 2.

FIG. 7B is a close-up view of the second retention structure of thestent of FIG. 2 with a retrieval string through the eyelet.

FIG. 8 shows a coronal view of the stent of FIG. 1 with the secondretention structure positioned in a renal pelvis of a kidney and thefirst retention structure positioned in the bladder of a person.

FIG. 9 shows a coronal view of the stent of FIG. 1 with the firstretention structure positioned in a renal pelvis of a kidney and thesecond retention structure positioned in the bladder with a retrievalsuture positioned through the eyelet of the second retention structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2A is a perspective view of a stent 100 comprising a tubular member102 and a lumen 103 (see FIG. 4) extending through the tubular member102. At opposite ends of tubular member 102 are a first retentionstructure 104 and a second retention structure 106 with an intermediateportion 114 extending between the two. First retention structure 104 andsecond retention structure 106 are used to position one end of stent 100in the renal pelvis of the kidney and the other end of stent 100 in thebladder with intermediate portion 114 extending in the ureter to preventmigration of stent 100 out of these areas.

First retention structure 104 is formed by bending an end of tubularmember 102 into multiple coils 108. The illustrated embodiment showsfive coils 108 a-108 e, but any number of coils 108 can be included. Oneskilled in the art would also recognize that at least two coils 108 a,108 b is preferred. Multiple coils 108 are each formed by shaping theend of tubular member 102 into multiple spiral coils each having thesame diameter and wound about an axis 109 to provide an anchor for stent100. It could also be possible, however, to form multiple coils 108 byshaping the end of tubular member 102 into a multiple turn, spiralplanar coil formed with multiple turns wound upon each other within thesame plane about the same or common axis. This implementation leads tocoils having increasingly larger diameters, but leads to more materialinside the body.

Second retention structure 106 is formed by bending an end of tubularmember 102 into a coil 110 around an axis 112. Coil 110 is formed byshaping the end of tubular member 102 in a turn. It could also bepossible to form second retention structure 106 with multiple coils inthe manner described above so that each end of tubular member 102 hasmultiple coils.

The first coil 108 a of multiple coils 108 of first retention structure104 and coil 110 of second retention structure 106 have the sameconstruction. Each structure is formed around its respective axes 109,112 that is orthogonal to and offset from an axis extending throughintermediate portion 114 of stent 100 in the direction of flow. Thus,first coil 108 a of first retention structure 104 and coil 110 of secondretention structure 106 are offset from the axis extending throughintermediate portion 114 and lead tangentially into intermediate portion114 on opposite sides. Moreover, while first coil 108 a of firstretention structure 104 and coil 110 of second retention structure 106can lie in a single plane that is common with intermediate portion 114,second coil 108 b, third coil 108 c, fourth coil 108 d, and fifth coil108 e can lie in successively offset planes so that each of the multiplecoils 108 can have a substantially similar diameter. A substantiallysimilar diameter is defined as a diameter that is generally less thantwo times the outer diameter of tubular member 102, which is the overalldiameter increase if a successive coil was coiled around an inner coil.

FIG. 2B shows another example of a stent 100 comprising a tubular member102 and a lumen 103 extending through the tubular member 102. Atopposite ends of tubular member 102 are a first retention structure 104and a second retention structure 106 with an intermediate portion 114extending between the two. First retention structure 104 is formed bybending an end of tubular member 102 into multiple coils 108. Theillustrated embodiment shows five coils 108 a-108 e wound aboutseparate, unique axes 109 a-109 e. Multiple coils 108 are each formed byshaping the end of tubular member 102 into multiple spiral coils of thesame diameter each wound about separate axes 109 a-109 e to provide ananchor for stent 100.

FIG. 3 shows stent 100 constructed in accordance with this disclosurethat also includes an anti-coiling layer 120 over first retentionstructure 104 to present multiple coils 108 as an elongated extension122 of tubular member 102. This allows the surgeon to use a stentstripper 200 (shown in FIG. 5B) intraoperatively to remove a segment ofanti-coiling layer 120 resulting in stent 100 of a desired length butwith at least one coil 108 e of multiple coils 108 a-108 e. As shown inFIG. 5B, stent stripper 200 placed in position where a stripping actionin the direction of the arrows will remove the corresponding portion ofanti-coiling layer 120. Any redundant coils 108 b-108 e can then betrimmed using scissors in the operating room resulting in a stent of thedesired length with minimal redundant indwelling stent-material. In thismanner, if only a small portion of the anti-coil polymer 120 is removed,stent 100 could accommodate a very tall patient. Likewise, if themajority of the anti-coiling layer 120 is removed, and the resultantredundant coils 108 b-108 e are trimmed off, stent 100 could accommodatea pediatric patient or a patient of short stature.

In accordance with an aspect of this disclosure, multiple indices 124a-124 e are spaced along elongated extension 122 of tubular member 102that correspond with coils 108 a-108 e of multiple coils 108 on firstretention structure 104. Indices 124 a-124 e enable the physician todetermine the extent to which multiple coils 108 in first retentionstructure 104 unwrap when the corresponding amount of anti-coiling layer120 is removed.

FIG. 4 shows a cross section of the stent 100 with the anti-coilinglayer 120. The tubular member 102 surrounds lumen 103. The anti-coilinglayer 120 coats a portion corresponding to elongated extension 122 oftubular member 102.

FIGS. 5A-5D shows the above-described process more clearly. FIG. 5Ashows a perspective view of stent 100 as it would appear out of itspackaging. Stent 100 presents second retention structure 106 at one endwith tubular member 102 extending between second retention structure 106and elongated extension 122 of tubular member 102 at the other end. Thesurgeon approximates the desired length of stent 100 with reference tothe corresponding indices 124 a-124 e and positions a stent stripper 200in the appropriate position, as shown in FIG. 5B. Stent stripper 200creates a circumferential cut through anti-coiling layer 120 withoutpenetrating tubular member 102. Anti-coiling polymer 120 is removedbeginning at the location of the cut through the end of first retentionstructure 104 leaving at least one coil 108 e of multiple coils 108, orin the illustrated process coils 108 d and 108 e of multiple coils 108.In this situation, coil 108 e is a redundant coil, as shown in FIG. 5C.The physician then uses standard operating room scissors to trimredundant coil 108 e to create the desired length of stent 100. Theremaining stent 100 is the desired length with a single, standard coil108 d on first retention structure 104.

Indices 124 a-124 e can be visual markings along stent 100 for locatinga stent stripper 200 or, as shown in FIG. 6C-6D, they could be a seriesof circumferential perforations 126 of a predetermined thickness. Thesecircumferential perforations 126 would allow the surgeon to remove theanti-coiling layer 120 at the predetermined location. Thisimplementation is similar to the proceeding where FIG. 6A shows stent100 before anti-coiling layer 120 is applied and FIG. 6B shows stent 100with anti-coiling layer 120. Anti-coiling polymer 120 iscircumferentially perforated at predetermined intervals. Thesecircumferential perforations 126 of anti-coiling layer 120 can bestripped from the stent manually at one of the premade circumferentialperforations 126 rather than requiring stent stripper 200. The physicianthen manually strips anti-coiling layer 120 off of the remaining lengthof stent 100. By removing the anti-coiling layer 120, the end for firstretention structure 104 of stent 100 presents coil 108 d as firstretention structure 104 with redundant coil 108 e being trimmed off bythe surgeon, as discussed above.

As described in FIG. 1, stent 11 of the prior art is designed in apolarized fashion with tapered tip 13 on the proximal portion 32 thatfacilitates passage beyond the obstructive pathology in ureter 18.Distal portion 15 is generally designed with retrieval string 35attached to bladder retention coil 24. This retrieval string 35 is leftemanating from urethra 38 and can be extracted by the patient at apredetermined period of time. Clinically, these two features are rarelyutilized together in any individual surgical case. These two featuresare used separately depending on the procedure. As an example, if apatient with an obstructive ureteral stone presents with sepsis thepatient needs urgent ureteral stent placement. In this case, tapered tip13 is useful for navigating stent 11 beyond the obstructive process.Retrieval string 35 would not be utilized because the patient would needa second procedure to treat the stone after the infection has resolved.This second procedure usually involves ureteroscopic manipulation withfragmentation and removal of the stone. Ureteroscopic manipulation cancause postoperative ureteral swelling which can result in transientureteral obstruction. For this reason, a ureteral stent is often leftpostoperatively. In this case, tapered tip 13 is not necessary since theprimary obstructive process is resolved, but retrieval string 35 can beuseful for removal of stent 11 after ureteral swelling has resolved.

This disclosure exploits this duality of indications by utilizing, asshown in FIG. 7A-7B, a tapered tip 128 with an eyelet 130 on coil 110 ofsecond retention structure 106 that can be utilized in either of theabove scenarios simply by inverting stent 100. FIG. 7B shows a retrievalstring 132 through eyelet 130. When retrieval string 132 is desired, thesurgeon simply passes a standard operating room suture through eyelet130 and out of an opening 134 of stent 100. The surgeon can then tie thesuture to itself to function as retrieval string 132.

FIG. 8 shows the deployment of second retention structure 106 withtapered tip 128 maneuvered beyond an obstructing stone 95 in ureter 18.In this case, there is no need for retrieval string 132 since stone 95must be treated with a second procedure at a later date. Tapered tip 128of second retention structure 106 is navigated beyond stone 95 andresides in renal pelvis 14.

FIG. 9 shows the deployment of second retention structure 106 withtapered tip 128 after ureteroscopic manipulation. In this case, theprimary obstructive process (ureteral stone 95) has been treated andstent 100 is left in place because postoperative ureteral swelling isanticipated. Tapered tip 128 is not needed to navigate stent 100 torenal pelvis 14, thus the physician places retrieval string 132 througheyelet 130 and out opening 134 on at the end of second retentionstructure 106 and places stent 100 in an inverted fashion with taperedtip 128 in the bladder 20. This dual tapered tip 128 and eyelet 130feature addresses the benefit of a polarized stent design but allows oneend of stent 100 to remain modifiable as discussed above.

Ureteral stent 100 can be formed of biocompatible shape memory tubingcomprising a polymer, polyurethane, silicone, nitinol or otherbiocompatible material. Multiple coils 108 on first retention structure104 can be straightened over a wire or forced to configure a coil shapedirectly opposing the desired orientation of multiple coils 108. Whilein this position, all or a portion of stent 100 is coated withanti-coiling layer 120 such that multiple coils 108 are completelystraightened when stent 100 is in its native form. This createselongated extension 122 extending from hollow tubular member 102 alonger length lacking without presenting an opposing coil untilanti-coiling layer 120 is removed.

Anti-coiling polymer 120 can be a polymer, polyurethane, silicone,nitinol or any other type of biocompatible material that resistscoiling. Stent 100 can include a thin exterior lubricous coating tofacilitate the placement of the stent 100. The interior surface ofhollow tubular member 102 could also be coated with a lubricous coating.Ureteral stent 100 can also include a series of drainage holes formedthrough tubular member 102 and at various locations thereby to admiturine or other fluids into a tubular member 102 for transport to bladder20 past any obstruction in ureter 18.

The stent herein describe has a completely modifiable length and theability to trim redundant stent material. This affords the physician theability to intraoperatively place a stent of the ideal length, using asingle product, for every patient. The invention also significantlydecreases hospital stent inventory, since only varied stent diameterwould need to be inventoried. It has the added benefit of being able toaccommodate ureteral lengths at the extremes that almost universally arenot inventoried by hospitals.

While this disclosure is directed to a stent 100 used in the ureter, oneskilled in the art would recognize that the structure and methodsdisclosed herein relate to any type of drainage tubes used to divertfluid from viscus structures of the body and is applicable to anydrainage tube where an adjustable length is desired. For simplicity, themain embodiment in the form of a ureteral stent is depicted anddescribed. Other potential embodiments include other drainage devicesused within viscus structures such as ventriculoperitoneal shunts,nephrostomy tubes, gastrostomy tubes, cholecystostomy tubes, etc.

While the principles of the invention have been described herein, it isto be understood by those skilled in the art that this description ismade only by way of example and not as a limitation as to the scope ofthe invention. Other embodiments are contemplated within the scope ofthe present invention in addition to the exemplary embodiments shown anddescribed herein. Modifications and substitutions by one of ordinaryskill in the art are considered to be within the scope of the presentinvention, which is not to be limited except by the following claims.

We claim:
 1. A stent comprising: a tubular member; a first retentionstructure at one end of the tubular member comprising multiple coilseach of which has substantially the same diameter to provide an anchorfor the stent; a second retention structure at an opposite end of thetubular member; and a lumen extending through the tubular member, thefirst retention structure and the second retention structure.
 2. Thestent of claim 1, and further comprising a removable anti-coilingmaterial over the multiple coils of the first retention structure topresent the multiple coils as an elongated extension of the tubularmember, whereupon removal of the removable anti-coiling material atleast one of the multiple coils of the first retention structure ispresented.
 3. The stent of claim 2, and further comprising multipleindices on the elongated extension of the tubular member each of whichdemarcate a corresponding one of the multiple coils of the firstretention structure.
 4. The stent of claim 3, wherein the multipleindices are each circumferential perforations in the anti-coilingmaterial that enables a stripping away of the anti-coiling material. 5.The stent of claim 4, wherein the multiple indices are each visualmarkings.
 6. The stent of claim 5, wherein the anti-coiling material isadapted for removal beginning from one of the multiple indices to an endof the elongated extension of the tubular member to present at least onecoil of the multiple coils of the first retention structure, and whereinone or more of the multiple coils is trimmable at a predeterminedlocation to remove at least one coil from the multiple coils of thefirst retention structure to present a single coil of the multiple coilsof the first retention structure.
 7. The stent of claim 1, and furthercomprising a distal end on the second retention structure and a taperedtip on the distal end adapted for maneuvering the second retentionstructure past an obstruction.
 8. The stent of claim 7, and furthercomprising an eyelet on the distal end of the tapered tip for receivinga suture.
 9. The stent of claim 1, wherein each coil is wound about aseparate axis.
 10. A stent comprising: a tubular member; a firstretention structure and a second retention structure at opposite ends ofthe tubular member, wherein the first retention structure furthercomprises multiple coils; a lumen extending through the tubular member,the first retention structure and the second retention structure; and aremovable anti-coiling material over the multiple coils of the firstretention structure to present the multiple coils as an elongatedextension of the tubular member, whereupon removal of the removableanti-coiling material at least one of the multiple coils of the firstretention structure is presented.
 11. The stent of claim 10 wherein eachcoil of the multiple coils is wound about a separate axis to provide ananchor for the stent.
 12. The stent of claim 10, and further comprisingmultiple indices on the elongated extension of the tubular member, eachof which demarcate a corresponding one of the multiple coils of thefirst retention structure.
 13. The stent of claim 12, wherein themultiple indices are each visual markings.
 14. The stent of claim 12,wherein the multiple indices are each circumferential perforations inthe anti-coiling material that enables a stripping away of theanti-coiling material.
 15. The stent of claim 10, wherein theanti-coiling material is adapted for removal beginning from one of themultiple indices to an end of the elongated extension of the tubularmember to present at least one coil of the multiple coils of the firstretention structure, and wherein one or more of the multiple coils istrimmable at a predetermined location to remove at least one coil fromthe multiple coils of the first retention structure to present a singlecoil of the multiple coils of the first retention structure.
 16. Thestent of claim 10, and further comprising a distal end on the secondretention structure and a tapered tip on the distal end.
 17. The stentof claim 16, and further comprising an eyelet on the distal end of thetapered tip for receiving a suture.
 18. The stent of claim 10, whereineach coil of the multiple coils is wound about a common axis to providean anchor for the stent.